These days, in the field of computers and electronic devices, operations performed using the contents displayed on a display device, rather than using buttons, have been increasingly developed. To perform such operations, a touch switch is arranged at the front side of the display device, and a touch position is detected. The types of touch switches include a resistive type, a surface acoustic wave type, an infrared type, and the like. There is also a capacitive type, in which a position is detected by a variation in capacitance caused by a touch of a finger and/or proximity of a finger. For example, Patent Literature 1 discloses a capacitive touch switch having a matrix electrode (a two-layer structure in X-direction and Y-direction), as shown in FIGS. 19 and 20.
A detailed description is provided with reference to FIG. 21, which is a schematic plan diagram schematically showing the structure of a capacitive touch switch as described above; and FIG. 22, which is a cross-sectional view of the structure. A known capacitive touch switch 400 comprises a first planar body 403 having a substrate 401 and transparent first electrodes 402 comprising ITO, and arranged in a strip pattern on one side of the substrate 401; and a second planar body 406 having a substrate 404 and transparent second electrodes 405 comprising ITO, and arranged in a strip pattern on one side of the substrate 404. The first planar body 403 and the second planar body 406 are bonded via an adhesive layer 407 in such a manner that the first electrodes and second electrodes face each other.
When an arbitrary position on the planar body is touched with a finger or the like, the electrodes 402 and 405 detect a change in the voltage or the like based on the capacitance of a human body at the contact position, and a coordinate of the contact position is thereby calculated.
However, the resistivity of ITO is high, usually 200Ω/□ to 1000Ω/□. This results in an increase in the size of the touch switch, along with an increase in the resistance between terminals of the electrodes. This reduces the detection sensitivity of the capacitance, and disables the operation of the touch switch.
Further, Patent Literature 2 discloses a capacitive touch switch that does not use ITO. A copper or copper-alloy electrode is formed in a mesh pattern, thereby allowing the transmission of the electrode to be 70% or higher. A low-resistance electrode is formed while maintaining the visibility.
However, the electrodes in Patent Literature 2 are only provided on one side of the substrate. When two layers of electrodes are formed using the first electrodes and the second electrodes, as described in Patent Literature 1, the visibility will be reduced when the first planar body is overlapped with the second planar body.